Changes
- Fixed custom PNG sleep images falling back to the default
Sleepingscreen after reading a book by splitting PNGdec's configured scanline storage from its decoder object: the ESP32-C3 now makes two smaller allocations instead of requiring one contiguous 59 KB heap block, while retaining wide-PNG support inside EPUBs. - Released reader-only memory before custom-directory enumeration, deferred state persistence until after sleep rendering, made PNG use the same
Entering sleeptransition as BMP, closed files on decoder-initialization errors, advanced the custom-image sequence only after a successful render, and persisted failure-stage heap diagnostics.